function x = num_mutation_ben(x,pm)

if rand < pm
    for m=1:30
        x(:,m) = x(:,m) + (1-2*rand) * 10e-2 ;
    end
        
    %x= x + [(1-2*rand) * 10e-3  (1-2*rand) * 10e-3 ];
end
